This invention relates to water supply freeze avoidance devices for municipal or other water supply tanks. In northern climates of the United States, there are many small towns which have municipal water supplies contained within tanks mounted upon elevated towers. Because of the nature of small town life, the volume of water drawn from the water tower during late night and early morning hours is quite small. Because of this, many small municipalites are confronted with the annual problem of the water supply within the water tower tank freezing over, resulting in the necessity to defrost the water tower with steam or other heating means at considerable expense and inconvenience. Because little if any discharge of water from the water supply tank occurs during nighttime hours, the water in tanks is allowed to become still and freezing occurs on top of the water supply and along the tank walls. Ice layers as much as six feet thick have been experienced. When the water tower supply fully freezes over, it is difficult to draw water from the tank, even though elevated, due to the differential air pressures between the outlet pipe and the top of the water supply under the ice cap.
When steam heating means are employed to de-ice the water tower, handlers of the steam equipment must climb the tower and supply heated steam to the tank walls and ice cap covering the water supply. Such work is dangerous, unpleasant, and expensive for the municipality.
An alternative method employed by smaller towns in dealing with the freezing problem is to allow a continual water discharge from the water tower into city sewers or through the overflow drain onto the ground. In some instances, the overflow drain spills water directly out of the tank resulting in an ice build-up at the base and legs of the water tower. With either of these methods, water is wasted, along with the power needs of the main system pump in continually filling the water tank.
Water supplies in large municipalities do not suffer from problems of this degree because of their larger populations and the likelihood that the water supply will be utilized both night and day. Furthermore, water towers of recent vintage are employed with an agitation system to provide a source of continually moving water into the tank which operates whether it is winter or summer.